This invention relates to a subscriber access apparatus adapting local access networks in which subscribers directly participates, to public network, such as ATM Core Network. Such apparatus is also called a subscriber access node. In particular, this invention relates to a novel subscriber access apparatus or node.
A recent trend has been directed to technologies which delivers high bandwidth data signals over existing copper wiring provided by the telephone companies, and such technologies are referred to as digital subscriber line (DSL) technologies.
DSL technologies are generally categorized into four types of Asymmetric DSL (ADSL), High-data-rate DSL (HDSL), Single-line DSL (SDSL) and Very-high-data-rate DSL (VDSL). On the other hand, xDSL is used as a group term referring to ADSL, HDSL, SDSL and VDSL.
Specifically, ADSL technology uses ADSL modem in compliance with ANSI T1.413 and is designed so that a wide bandwidth is assigned to a downstream direction (from the central office to the customer site) in comparison with an upstream direction. For example, downstream bandwidth ranges from 1.5 to 9 Mbps, while upstream bandwidth ranges from 16 to 640 kbps.
Over access networks based on such xDSL technologies, ATM cells can be directly transported. Herein, access networks based on xDSL technologies are also called xDSL access networks. For the purpose of such transporting, various proposals have been made about transport configurations, architectures and interfaces for ATM. For example, ADSL Forum provides technical reports about the above proposals on their web site.
On the contrary to such xDSL technologies, over other access networks based on general analog communication and Narrow-band ISDN (N-ISDN), ATM cells could not directly be transported. Herein, access networks of general analog communication and ISDN are called analog communication access networks and ISDN access networks, respectively. For analog communication or ISDN, subscriber access apparatuses for STM, STM exchanges and STM-ATM mutual converters are, therefore, required to adapt between ATM Core Network and these access networks of analog communication or N-ISDN,
As a result, subscriber access apparatuses of types different from each other should be located in local access networks That is, STM subscriber access apparatuses are connected to analog commutation access networks or ISDN access networks, while ATM subscriber access apparatuses are connected to xDSL access networks.
As other techniques relating to the above topics, JP-A Nos. 6-197118 and 6-197119 disclose subscriber access apparatuses which can adapt ATM Core Network directly over the analog communication access network, such as a telephone commutation access network. In addition, JP-A No. 6-276219 also discloses a subscriber access apparatus which can adapt ATM Core Network directly over the ISDN access network.
However, JP-A Nos. 6-197118, 6-197119 and 6-276219 do not take xDSL technologies into consideration and these apparatuses can not handle xDSL signal, accordingly. Therefore, subscriber access apparatuses which are different in structure from each other should be prepared each of xDSL access networks and the others, even though these techniques are proposed.
This invention, therefore, provides a subscriber access apparatus for use in common to all of analog communication access networks, ISDN access networks and xDSL access networks. Such apparatus is connected, on a downstream side, to these access networks and is connected, on a upstream side, to the ATM Core Network.
According to one aspect of this invention, the subscriber access apparatus comprises an analog-SLIC, an ISDN-SLIC, an xDSL-SLIC, a signal processor and a controller. Herein, SLIC stands for subscriber line interface circuit.
The analog-SLIC is connected, on the downstream side, to an analog communication line which is for analog signals and which is included in the analog communication access network. Such analog-SLIC carries out mutual conversion between the analog signals and pulse code modulation (PCM) signals.
The ISDN-SLIC is connected, on the downstream side, to an ISDN line which is for ISDN data signals including B-channel data signals and which is included in the ISDN access network. Such ISDN-SLIC extracts, on the downstream side, the B-channel data signals from the ISDN data signals to produce the B-channel data signals as digital data signals. On the other hand, the ISDN-SLIC produces the ISDN data signals having the B-channel data signals corresponding to the digital data signals on the upstream side.
The xDSL-SLIC is connected, on the downstream side, to an xDSL line which is for xDSL signals and which is included in the xDSL access network. Such xDSL-SLIC splits, on the downstream side, the xDSL signals into high and low frequency data signals. On the other hand, the xDSL-SLIC produces the xDSL signals from the high and low frequency data signals on the upstream side.
The signal processor is connected, on the upstream side, to the ATM Core Network which includes ATM exchange, and so on, and which transfers ATM cells each having a header and a payload on the ATM Core Network. Such signal processor processes, on the downstream side, the PCM signals, digital data signals and high and low frequency data signals in response to a first control signal to produce the ATM cells obtained by mapping the PCM signals, the digital data signals and the high and low frequency data signals into payloads of the ATM cells. On the other hand, the signal processor processes, on the upstream side, the ATM cells in response to a second control signal to divide the ATM cells into the PCM signals, the digital data signals, the high and low frequency data signals.
The controller monitors the analog-SLIC, the ISDN-SLIC, the xDSL-SLIC and the signal processor. Besides that, the controller produces the first control signal in response to at least one of the analog signals, the ISDN data signals and the xDSL signals. That is, when the analog-SLIC receives the analog signal, the controller detects it and produces the first control signal. And also, when the ISDN-SLIC or the xDSL-SLIC receive the ISDN data signals or the xDSL signals, respectively, the controller detects it and produces the first control signal. On the other hand, the controller produces the second control signal when the signal processor receives the ATM cells from the ATM Core Network.
Specifically, in such apparatus, the xDSL-SLIC may be an ADSL-SLIC to be connected, through an ADSL line as the xDSL line, to an ADSL modem in compliance with ANSI T1.413 standard. Herein, the ADSL line is used for an ADSL signals as the xDSL signals.
Furthermore, in such apparatus, the signal processor may comprise a time switch, a CLAD device and an ATM network interface circuit, as the followings.
The time switch receives, on the downstream side, the PCM signals, the digital data signals and the low frequency data signals and then makes upward switch-paths to produce intermediate data signals, in response to the first control signal. On the other hand, the time switch receives, on the upstream side, the intermediate data signals and then makes downward switch-paths to produce the PCM signals, the digital data signals and the low frequency data signals, in response to the second control signal.
The CLAD device receives, on the downstream side, the intermediate data signals and the high frequency data signals and then assembles the ATM cells, in response to the first control signal. On the other hand, the CLAD device receives, on the upstream side, the ATM cells and then disassembles the ATM cells to produce the high frequency data signals and the intermediate data signals, in response to the second control signal.
The ATM network interface circuit is used in case where the ATM Core network has an interface to be connected to a synchronous optical network (SONET), and receives the ATM cells and maps the ATM cells to the interface of the SONET.